IT Companies Ireland

 Extracted from http://makeitinireland.com/tech-map/ using js in google chrome console
 
 $(".article").each(function(){
console.log($(this).find("h3").html() + " -- "+ $(this).find("#company_size").html() + " -- " + $(this).find("#company_address").html()); 
});

Company name -- Company size -- Company address

 Synchronoss Software Ireland Ltd. -- Mid-sized Company --  The Academy, 42 Pearse St.,  Dublin 2
 Fishtree -- Startup --  Fumbally Lane,  Dublin
 Dropbox -- Multinational --  One Park Place, Hatch St Upper,  Dublin
 Fenergo -- Mid-sized Company --  Ormond House, Ormond Quay,  Dublin 7
 Instagram -- Multinational --  Dufferin Ave,  Dublin
 Tyco -- Multinational --  City Gate, Mahon,  Cork
 Bank Of America Merrill Lynch -- Multinational --  Central Park Leopardstown,  Dublin
 Signatur -- Startup --  NDRC, Digital Exchange, Crane Street,  Dublin 8
 Airbnb -- Mid-sized Company --  South Lotts Street,  Dublin 4
 New Relic -- Mid-sized Company --  34-39 Nassau Street,  Dublin 2
 Full Tilt -- Mid-sized Company --  Block AD, 3rd Floor, Cherrywood Science   Technology Park, Loughlinstown,  Dublin 18
 CodeFirst -- Startup --  77 Sir John Rogerson's Quay,  Dublin 2
 HEAnet -- Mid-sized Company --  5 George's Dock, IFSC,  Dublin
 GillSoft Limited -- Startup --  Liffey Row, Liffey Valley Park, Lucan,  Dublin
 Zendesk -- Mid-sized Company --  1 Grand Parade,  Dublin
 Learnosity -- Startup --  Business   Research Centre, National College of Ireland,  Dublin
 D4H Technologies -- Startup --  The Baily Lighthouse,  Howth
 Digital Stream -- Startup --  Digital Hub,  Dublin
 Amdocs -- Multinational --  Blackthorn Road,  Dublin
 Grandson -- Startup --  12 Roden Place,  Dundalk
 Thinkhouse -- Startup --  Fumbally Lane,  Dublin 8
 Gaumina : Digital Agency -- Mid-sized Company --  10-13 Thomas Street,  The Digital Hub, Dublin 8
 GCO Solutions -- Startup --  45 Dublin Road,  Dundalk
 SumUp Ltd. -- Startup --  Cumberland Street South,  Dublin 2
 Carma -- Startup --  Penrose Wharf, 2nd Floor Alfred St,  Cork
 Amriss -- Startup --  Synergy Centre,  Tallaght, Dublin 24
 Texuna Technologies Ltd -- Startup --  Unit 8 Hollyhill Industrial Estate,  Cork
 aqmetrics -- Startup --  Unit 14F, Maynooth Business Campus,  Maynooth
 Amasat Ltd -- Startup --  57, Block D, Hanover Dock, Hanover Quay, Forbes Street,  Dublin
 Kill The Loop -- Startup --  64 Sapphire, The Grange, Brewery Road, Blackrock,  Dublin
 LikeCharity -- Startup --  23 South William Street,  Dublin
 Tribal -- Startup --  23 South William Street,  Dublin 2
 Midas Technologies -- Startup --  Clonmore Business   Technology Park,  Mullingar
 Sláinte Healthcare -- Mid-sized Company --  The Cubes Offices, Beacon South Qtr Sandyford,  Dublin 18
 LogMeIn -- Mid-sized Company --  Blood Stoney Road,  Dublin
 TecSupport -- Startup --  U6,Galway Technology Centre, Mervue Busines Park,  Galway
 Spanish Point Technologies Ltd. -- Startup --  32 Sir John Rogersons Quay,  Dublin
 CashAnalytics -- Startup --  12 Hume Street,  Dublin 2
 Redhills Software -- Startup --  12 Hume Street,  Dublin 2
 Sian's Plan -- Startup --  51 Malone Road,  Belfast
 Iconic Translation Machines Ltd. -- Startup --  Collin's Avenue,  Dublin
 Groupon International Ltd. -- Multinational --  Harcourt Road,  Dublin
 Gilt -- Multinational --  The Anchorage, 17-19 Sir John Rogerson's Quay,  Dublin
 Yellow Zebra Digital -- Startup --  2 Haddington Road,  Dubin
 Monex Financial Services -- Mid-sized Company --  KTI Centre, Deerpark,  Killarney
 OralEye -- Startup --  17 Trinity Street,  Dublin 2
 Ircona -- Startup --  Unit 4B-1, Blanchardstown Corporate Park,  Dublin 15
 Electronic Recycling -- Startup --  Unit 20, jamestown Business Pk, Finglas,  Dublin 11
 Converser -- Startup --  2 Crown Alley,  Dublin 2
 Rumble Labs -- Startup --  46 Hill St, Belfast, BT1 2LB,  Belfast
 Westbourne I.T. -- Mid-sized Company --  Unit 5, Citylink Business Park, Forge Hill,  Cork
 plugMEDIA -- Startup --  Digital Depot, Roe Lane, Thomas Street,  Dublin 8
 Amazon -- Multinational --  1 Kilmainham Sq, Inchicore Rd, Dublin, 8,  Dublin
 Digital Marketing Institute -- Startup --  Marina House, 11-13 Clarence Street,  Dun Laoghaire
 Red Hat -- Multinational --  6700 Cork Airport Business Park Phase II 1st Floor,  Cork
 Aonach -- Startup --  Kilmurry,  Kenmare
 Software Design -- Startup --  The Digital Court, Rainsford Street,  Dublin
 Critical Path -- Mid-sized Company --  42 - 47 Lower Mount Street,  Dublin
 Espion  Ltd -- Mid-sized Company --  Corrig Road, Corrig Court,  Sandyford Ind Estate
 Distilled Media -- Mid-sized Company --  Latin Hall, Golden Lane,  Dublin 8
 Software Design -- Startup --  The Digital Court, Rainsford Steet,  Dublin
 ACI Worldwide -- Startup --  Lanmark Building, Lonsdale Road, National Technology Park,  Limerick
 Smarttech -- Mid-sized Company --  Unit 8 Cleve Business Park Mohanan Road Cork, Ireland,  Cork
 Vconnecta -- Startup --  Western Gateway Building Western Rd,  Cork
 Go2mobile Solutions -- Startup --  Roselawn House,  Limerick
 Formula Networks -- Startup --  3B1 Western Business Park,  Shannon
 StudioForty9 -- Startup --  34 Grand Parade,  Cork City
 Bandwidth Telecommunications Limited -- Startup --  25 Finglas Business Park,  Dublin 11
 Storm Technology Ltd. -- Mid-sized Company --  511 The Capel Building Mary's Abbey,  Dublin 7
 hostelbench -- Startup --  Docklands Innovation Park, 128-130 East Wall Road,  Dublin
 CampusIT -- Startup --  Clanwilliam Place,  Dublin 2
 Dovetail -- Startup --  Taylor's Lane, Maryland,  Dublin
 Acumenx -- Startup --  The Rubicon Centre,  CIT Campus, Cork
 Movidius -- Startup --  19 Mountjoy Square,  Dublin
 Cloudium Systems -- Startup --  George's Quay,  Limerick
 10gen (the MongoDB company) -- Mid-sized Company --  5th Floor Latin Hall Golden Lane,  Dublin 8
 FIT Ltd. -- Startup --  7a Bellevue Industrial Estate, Glasnevin,  Dublin
 Mercury Digital -- Startup --  The Digital Depot, Thomas St, Dublin 8,  Dublin
 Global Shares -- Mid-sized Company --  West Cork Technology Park, Clonakilty,  Cork
 SPARK Marketing Communications -- Startup --  100 O'Connell Street,  Limerick
 Monitor Backlinks Ltd. -- Startup --  17 Upper Pembroke Street,  Dublin 2
 Cloud Compare -- Startup --  Unit 23 Northwood Court, Santry, Dublin 9,  Dublin
 LouderVoice -- Startup --  12 The Priory,  Old Chapel, Bandon, Co Cork
 SolarPrint -- Startup --  Ballymoss Road, Sandyford,  Dublin 18
 Aurion Learning  -- Startup --  475 Ormeau Road ,  Belfast 
 Betapond  -- Startup --  Arclabs ,  Waterford 
 Tascomi  -- Startup --  3 Ballynahinch Street ,  Hillsborough 
 ShotClip Ltd -- Startup --  NDRC, Crane Street, Digital Hub,  Dublin 8
 Osgo Solutions -- Startup --  Suite 14, The Cubes Offices,  The Beacon SQ, Sandyford
 Quotefish -- Startup --  4 Fitzwilliam Terrace, Strand Road, Bray,  Wicklow, Ireland
 BlueChief Solutions -- Startup --  106/108 O'Connell St., Co. Limerick,  Limerick
 Murrion Software Limited -- Startup --  Link Road, Ballincollig,  Cork
 Camba.tv -- Startup --  Greenhills Rd, Kilpoole Hill,  Wicklow
 AirPOS Ltd -- Startup --  Caernarvon House,  19 Donegall Pass
 Strata3 Limited -- Startup --  10 Westland Square, Pearse Street,  Dublin 2
 DemonWare -- Mid-sized Company --  King's Inn House, Parnell Street,  Dublin 1
 Compliance   Risks -- Startup --  Unit 9, Eastgate Avenue, Eastgate Business Park,,  Little Island, Cork
 Aetopia -- Startup --  ECIT Institute,  Belfast
 Bizimply -- Startup --  NDRC, Crane St,  Dublin
 Bullet HQ -- Startup --  32 Nassau Street,  Dublin
 Logentries -- Startup --  35 Barrow Street,  Dublin
 Continuum -- Startup --  East Wall Road, Dublin 3,  Dublin
 LearnUpon -- Startup --  12 Hume Street,  Dublin
 Cluey.com -- Startup --  9-13 Blackhall Place,  Dublin 7
 Talentevo -- Startup --  Belfield Innovation Park, Dublin 4, Ireland,  Dublin
 Storyful -- Startup --  48 Lower Mount Street,  Ferry House
 Gnarly Adventure -- Startup --  Nexus Innovation Centre, University of Limerick,  Limerick
 Yellowschedule -- Startup --  Tierney Building, University of Limerick,  Limerick
 Boxever -- Startup --  The Warehouse,  Dublin
 Touch Communications -- Startup --  91,  Fairyfield
 MobaNode -- Startup --  91 O'Connell St,,  Limerick
 Global Business Register -- Startup --  Arclabs Research Center, WIT West Campus, Carriganore,  Waterford
 PropelAd -- Startup --  NCI Business Centre, Mayor Square,  Dublin
 Qstream -- Startup --  35 Barrow Street,  Dublin 4
 Guidecentral -- Startup --  Dogpatch Labs,  The Warehouse, 35 Barrow Street, Dublin 4
 Riffstation -- Startup --  35 Barrow Street,  Dublin
 Fluid Ui -- Startup --  Dogpatch Labs,  The Warehouse, 35 Barrow street, Dublin 4, Ireland
 SparkPage -- Startup --  Docklands Innovation Park, 128 – 130 Eastwall Road,  Dublin 3
 LinkedIn -- Multinational --  Wilton Plaza,  Dublin 2
 Cube Online Marketing -- Startup --  64 Lower Mount Street,  Dublin
 Text Republic -- Startup --  Kerry Technology Park,  Tralee
 Actus Mobile Solutions -- Startup --  Atlas Court,  IDA Business Park, Bray, County Wicklow
 RigBag -- Startup --  Kerry Technology Park,  Tralee
 Continuum -- Startup --  River House, East Wall Road,  Dublin 3
 Pledgup.com -- Startup --  Chambers House, Market Square,  Longford
 Esri Ireland -- Startup --  Navan Road,  Dublin
 Von Bismark -- Startup --  Crane Street, Dublin 8,  Dublin
 Paddy Power -- Multinational --  Belfield Office Park, Beech Hill Road, Clonskeagh, Dublin 4,,  Dublin
 Lumension -- Mid-sized Company --  Mervue Business Park,,  Galway
 Keelvar -- Startup --  Rubicon Centre,  Cork
 Web Summit -- Startup --  Mountpleasant Avenue,  Dublin
 ATOS -- Mid-sized Company --  Loughmahon Technology Park,  Cork
 Cauwill Technologies -- Startup --  HEAC, Unit 2, Moylish Park,,  Limerick
 MDG Web ltd -- Startup --  Dogpatch Labs, The Warehouse, 35 Barrow Street,  Dublin
 IIS -- Startup --  The Apex Building,  Blackthorn Road, Sandyford,  Dublin 18
 Encription Ireland Limited -- Startup --  Enterprise House, O'Brien Road,  Carlow 
 newsletter.ie -- Startup --  Lonsdale House, National Technology Park,  LIMERICK
 Cisco Systems, Inc. -- Multinational --  Oranmore Business Park,  Galway
 Shimmer -- Startup --  The Realtime Building, Clonshaugh Business and Technology Park,  Dublin
 Support Solutions -- Startup --  3013 lake drive citywest business campus,  Dublin
 Blacknight Internet Solutions Ltd -- Startup --  Unit 12A, Barrowside Business Par, Sleaty Road, Graiguecullen,  Carlow
 Big Red Cloud -- Startup --  Rathdown Hall,  Upper Glenageary Road
 Instant Opinion -- Startup --  11 Patrick Street,  Kilkenny
 Apple -- Multinational --  Hollyhill Industrial Estate, Hollyhill,  Cork
 Trustev -- Startup --  Block A, Heritage Business Park, Bessboro Road,  Cork
 Swrve -- Startup -- 9 Windsor Place, Pembroke Street Lower,,  Dublin
 Marketo -- Mid-sized Company -- Cairn House South County Business Park Leopardstown,  Dublin
 Make IT in Ireland -- Startup -- Eglington Street,  Cork
 Strencom -- Startup -- Heron House Blackpool Park, Blackpool Cork
 Statistical Solutions Ltd -- Startup -- 4500 Airport Business Park, Cork
 Solarwinds Software Europe Limited -- Multinational -- Unit 1101, Building 1000 City Gate, Mahon Cork
 SoftTrace -- Startup -- Barryscourt Business Park,Carrigtwohill, Co. Cork
 Smartech -- Startup -- 18-19 College Green, Dublin 2
 S3 Group -- Mid-sized Company -- Cork Business   Technology Park Model Farm Road, Cork
 Lincor Solutions Ltd. -- Mid-sized Company -- Cork Business and Technology Park Model Farm Road , Cork
 KineMatik Ltd. -- Startup -- Eastgate Hall Eastgate , Little Island, Co. Cork
 Kedington -- Mid-sized Company -- 9 Airways Technology Park Farmers Cross,Airport Road, Cork
 HiberniaEvros Technology Group -- Mid-sized Company -- 4 Eastgate Drive,Eastgate Business Park, Little Island, Cork
 Globetech Ltd -- Startup -- 1st Floor Unit I Building 6500 Cork Airport Business Park , Cork
 Firecomms -- Startup -- 2200 Airport Business Park Cork, Cork
 Exigent Networks -- Startup -- Eastgate House Eastgate Business Park, Little Island, Cork
 Eirteic Consulting -- Startup -- Eirteic Consulting Ltd.4th Floor, Centre Park House Centre Park Road, Cork
 Eirtech Communications -- Startup -- Heron House Blackpool Retail Park, Cork
 DigiSoft.tv -- Startup -- Building 4200 Cork Airport Business Park Kinsale Road, Cork
 Datalogix Solutions Ltd -- Startup -- Lough Mahon House,Skehard Road, Blackrock Cork
 CWSI -- Startup -- 11-12 St. Patrick's Quay, Cork
 Bard na nGleann -- Startup -- Unit A Béal Átha'n Ghaorthaidh , County Cork
 Avnet Client Solutions -- Startup -- National Software Centre, Loughmahon Technology Park, Mahon Cork
 AspiraCon -- Startup -- East Gate House, Little Island, Cork
 Akari Software Limited -- Startup -- 1 Eastgate Road, Little Island, Co. Cork
 Datalex -- Mid-sized Company -- Block U East Point Business Park, Dublin 3
 IT Alliance Group -- Mid-sized Company -- Park House North Circular Road, Dublin 7
 iQuate -- Mid-sized Company -- 4044 Kingswood Avenue CityWest National Digital Park, Dublin 24
 Mobile Travel Technologies Ltd. -- Mid-sized Company -- Digital Court Rainsford Street The Digital Hub, Dublin 8
 PMI Software Ltd -- Mid-sized Company --  Unit 8, Kingswood Avenue, City West Business Campus, Tallaght, Dublin
 Documatics (Irl.) Ltd -- Mid-sized Company -- The Rubicon Centre, Bishopstown, Cork
 Information Mosaic -- Mid-sized Company -- Styne House Upper Hatch Street, Dublin 2 
 Socrates Healthcare -- Mid-sized Company -- Protek House, Finisklin Business Park,, Sligo
 SL Controls Ltd -- Mid-sized Company -- Collooney IDA Industrial Park, Collooney, Co. Sligo
 Advanced Manufacturing Control Systems Ltd -- Mid-sized Company -- Fanningstown Crecora, Co. Limerick
 Mapflow Ltd -- Mid-sized Company -- O'Connell Bridge House, D'Olier St, Dublin 2 
 System Dynamics Ltd -- Mid-sized Company -- System Dynamics Group Limited Whitaker Court Sir John Rogerson's Quay, Dublin 2 
 Crest Solutions -- Mid-sized Company -- Waterfront Business Park, Little Island, Co. Cork
 Avego Limited -- Mid-sized Company -- Penrose Wharf 2nd Floor Alfred St.,, Cork
 Action Point -- Startup -- Lonsdale Road National Technology Park, Limerick
 Ergo -- Startup -- 1st Floor, Block T,East Point Business Park, Dublin 3
 Trilogy Technologies -- Mid-sized Company -- 2 Whitefriars, Aungier Street, Dublin 2
 MicksGarage.com -- Startup -- Unit 50 Park West Road Park West Industrial Park, Dublin 12
 Daysha Consulting -- Mid-sized Company -- 9 Mount Street Crescent, Dublin 2
 Version 1 -- Mid-sized Company -- Millennium House Millennium Walkway, Dublin 1
 Sentenial Ltd. -- Startup -- Unit 16F Maynooth Business Campus, Maynooth,Co. Kildare
 Ammeon -- Mid-sized Company -- O'Connell Bridge House, D'Olier St, Dublin 2
 Realex Payments -- Mid-sized Company -- The Observatory, 7-11 Sir John Rogerson's Quay, Dublin 2
 Vulcan Solutions -- Startup -- First Floor,Headford Point,Headford Road, Galway
 EMUTEX LTD -- Startup -- Axiom House, Raheen Business Park, Limerick
 The Now Factory -- Mid-sized Company -- Arkle Rd, Dublin, Co. Dublin
 ezetop -- Mid-sized Company -- 2nd Floor, Brooklawn House, Shelbourne Road, Dublin 4
 TERMINALFOUR Solutions Limited -- Mid-sized Company -- Second Floor, 110 Amiens Street, Dublin 1
 Enovation Solutions -- Startup -- The Friary Building, Bow Street, Dublin 7
 JD Edwards -- Multinational -- 25/28 North Wall Quay, Dublin 1
 PFH -- Mid-sized Company -- The Courtyard, Carmanhall Rd., Sandyford, Dublin 18
 JRI -- Multinational -- Innovation Works Kerry Technology Park, Tralee,Co. Kerry 
 Curam -- Mid-sized Company -- Unit 15 Joyce Way, Parkwest Business Park, Nangor Road, Dublin 12
 Openet -- Mid-sized Company -- 6 Beckett Way, Park West Business Park, Dublin 12
 Siemens -- Multinational -- Fitzwilliam Court Leeson Close, Dublin 2
 IAC -- Multinational -- Unit 1 College Business and Technology Park Blanchardstown North Road, Dublin 15
 Ericsson -- Multinational -- Beech Hill, Clonskeagh, Dublin 4
 Avaya -- Multinational -- The Atrium Block A Blackthorn Road Sandyford , Dublin 18
 HP -- Multinational -- Liffey Park Technology Campus Barnhall Road, Leixlip Co Kildare
 Sandisk -- Multinational -- Unit 100, Airside Business Park,Swords, County Dublin
 AOL -- Multinational -- The Brunel Building Heuston South Quarter, Dublin 8
 Yahoo -- Multinational -- Pinnacle One,East Point Business Park, Dublin 3
 Fujitsu -- Multinational -- Lakeshore Drive Airside Retail Park , Swords. Dublin
 SalesForce -- Multinational -- Level 1, Atrium A, Sandyford Business Park, Dublin 18
 SAP -- Multinational -- Block 11a Joyce Way Park West Business Park , Dublin 12
 Digit Games -- Startup -- 4 Prince’s Street, Dublin 2
 Havok -- Mid-sized Company -- 6-10 Suffolk Street, Dublin 2
 Zynga -- Multinational -- The Oval Building - Block I, Floor 3, 160 Shelbourne Road, Ballsbridge, Dublin 4
 Indeed.com -- Mid-sized Company -- 70 Sir John Rogerson’s Quay, Dublin 2
 HubSpot -- Mid-sized Company -- 2nd Floor 30 North Wall Quay, Dublin 1
 StoryToys -- Startup -- 27-29 Lower Pembroke Street , Dublin 2
 EngineYard -- Mid-sized Company -- 2nd Floor, 35 Barrow St., Dublin 4
 Blizzard -- Multinational -- The Atrium 5th Floor Blackpool Retail Park , Blackpool Co Cork
 Quantcast -- Mid-sized Company -- Glandore Business Centres Fitzwilliam Hall Fitzwilliam Place, Dublin 24
 Cisco -- Multinational -- Block P6,Eastpoint Business Park, Dublin 3
 Adobe -- Multinational -- 4-6 Riverwalk Citywest Business Campus, Dublin 24
 IBM -- Multinational -- Oldbrook House 24- 32 Pembroke Road Ballsbridge, Dublin 4
 Ebay -- Multinational -- 6b Blanchardstown Corporate Park,Blanchardstown, Dublin 15
 PayPal -- Multinational -- Ballycoolin Business Park, Dublin 15
 Microsoft -- Multinational -- Building 3, Carmanhall Road, Sandyford Industrial Estate , Dublin 18
 Oracle -- Multinational -- East Point Business Park Fairview, Dublin 3
 Intel -- Multinational -- Intel Ireland Ltd., Collinstown, Leixlip Kildare
 Symantec -- Multinational -- Ballycoolin Business Park Blanchardstown, Dublin 15
 Twitter -- Multinational -- , 
 Google -- Multinational -- Gordon House Barrow Street, Dublin 4
 Facebook -- Multinational --  Hanover Reach, 5/7 Hanover Quay, Dublin 2
 Trilogy Technologies -- Startup --  2 Whitefriars, Aungier Street, Dublin 2
 Tweak -- Startup -- Bank House Lower Bridge Street, Killorglin Co Kerry
 Nitrosell -- Startup -- Building 2100,Airport Business Park, Cork
 Newsweaver -- Mid-sized Company -- 2200 Airport Business Park, Kinsale Road Cork
 PFH -- Mid-sized Company -- 1 EastGate Avenue, EastGate Business Park, Little Island, Co.Cork
 Qumas -- Mid-sized Company -- QUMAS Cleve Business Park, Monahan Road, Cork
 TeamworkPM -- Startup -- North Point House,North Point Business Centre, Blackpool,Cork
 Zenith Technologies Ltd -- Startup -- Portgate Business Park,Ringaskiddy, Cork
 TreeMetrics -- Startup -- TreeMetrics Ltd.National Software Centre,NSC Campus,, Mahon, Cork
 Pilz -- Mid-sized Company -- Cork Business and Technology Park, Model Farm Road, Cork
 VoxPro -- Mid-sized Company -- Head Office Voxpro House, Riverview Business Park, Blackrock, Cork
 Amazon -- Multinational -- Cork Airport Business Park, Cork
 Dell -- Multinational -- 3rd floor, Building 2000, Citygate Business Park, Mahon Point, Cork
 McAfee -- Multinational -- Europe, Middle East and Africa (EMEA) Headquarters McAfee Ireland Ltd. Building 2000, City Gate, Mahon, Cork
 RedHat -- Multinational -- 6700 Cork Airport Business Park Phase II 1st Floor, Cork
 TrendMicro -- Multinational -- IDA Business   Technology Park, Cork
 Vmware -- Multinational -- Parnell House Barrack Square Main Street , Ballincollig Co. Cork
 EMC -- Multinational -- Ovens,  Co Cork
 Soundwave -- Startup -- 2nd Floor  60 Grand Canal,  Upper Dublin 04
 Zartis -- Startup --  Webworks Eglinton Street,  Cork

You could also add Genesys, US multinational with office in Galway.